source3/smbd/signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Signing Code
   4    Copyright (C) Jeremy Allison 2003.
   5    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
   6    Copyright (C) Stefan Metzmacher 2009
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23 #include "smbd/smbd.h"
  24 #include "smbd/globals.h"
  25 #include "../libcli/smb/smb_signing.h"
  26 #include "lib/param/param.h"
  27
  28 /***********************************************************
  29  Called to validate an incoming packet from the client.
  30 ************************************************************/
  31
  32 bool srv_check_sign_mac(struct smbd_server_connection *conn,
  33                         const char *inbuf, uint32_t *seqnum,
  34                         bool trusted_channel)
  35 {
  36         const uint8_t *inhdr;
  37         size_t len;
  38
  39         /* Check if it's a non-session message. */
  40         if(CVAL(inbuf,0)) {
  41                 return true;
  42         }
  43
  44         len = smb_len(inbuf);
  45         inhdr = (const uint8_t *)inbuf + NBT_HDR_SIZE;
  46
  47         if (trusted_channel) {
  48                 NTSTATUS status;
  49
  50                 if (len < (HDR_SS_FIELD + 8)) {
  51                         DEBUG(1,("smb_signing_check_pdu: Can't check signature "
  52                                  "on short packet! smb_len = %u\n",
  53                                  (unsigned)len));
  54                         return false;
  55                 }
  56
  57                 status = NT_STATUS(IVAL(inhdr, HDR_SS_FIELD + 4));
  58                 if (!NT_STATUS_IS_OK(status)) {
  59                         DEBUG(1,("smb_signing_check_pdu: trusted channel passed %s\n",
  60                                  nt_errstr(status)));
  61                         return false;
  62                 }
  63
  64                 *seqnum = IVAL(inhdr, HDR_SS_FIELD);
  65                 return true;
  66         }
  67
  68         *seqnum = smb_signing_next_seqnum(conn->smb1.signing_state, false);
  69         return smb_signing_check_pdu(conn->smb1.signing_state,
  70                                      inhdr, len,
  71                                      *seqnum);
  72 }
  73
  74 /***********************************************************
  75  Called to sign an outgoing packet to the client.
  76 ************************************************************/
  77
  78 void srv_calculate_sign_mac(struct smbd_server_connection *conn,
  79                             char *outbuf, uint32_t seqnum)
  80 {
  81         uint8_t *outhdr;
  82         size_t len;
  83
  84         /* Check if it's a non-session message. */
  85         if(CVAL(outbuf,0)) {
  86                 return;
  87         }
  88
  89         len = smb_len(outbuf);
  90         outhdr = (uint8_t *)outbuf + NBT_HDR_SIZE;
  91
  92         smb_signing_sign_pdu(conn->smb1.signing_state, outhdr, len, seqnum);
  93 }
  94
  95
  96 /***********************************************************
  97  Called to indicate a oneway request
  98 ************************************************************/
  99 void srv_cancel_sign_response(struct smbd_server_connection *conn)
 100 {
 101         smb_signing_cancel_reply(conn->smb1.signing_state, true);
 102 }
 103
 104 struct smbd_shm_signing {
 105         size_t shm_size;
 106         uint8_t *shm_pointer;
 107
 108         /* we know the signing engine will only allocate 2 chunks */
 109         uint8_t *ptr1;
 110         size_t len1;
 111         uint8_t *ptr2;
 112         size_t len2;
 113 };
 114
 115 static int smbd_shm_signing_destructor(struct smbd_shm_signing *s)
 116 {
 117         anonymous_shared_free(s->shm_pointer);
 118         return 0;
 119 }
 120
 121 static void *smbd_shm_signing_alloc(TALLOC_CTX *mem_ctx, size_t len)
 122 {
 123         struct smbd_shm_signing *s = talloc_get_type_abort(mem_ctx,
 124                                      struct smbd_shm_signing);
 125
 126         if (s->ptr1 == NULL) {
 127                 s->len1 = len;
 128                 if (len % 8) {
 129                         s->len1 += (8 - (len % 8));
 130                 }
 131                 if (s->len1 > s->shm_size) {
 132                         s->len1 = 0;
 133                         errno = ENOMEM;
 134                         return NULL;
 135                 }
 136                 s->ptr1 = s->shm_pointer;
 137                 return s->ptr1;
 138         }
 139
 140         if (s->ptr2 == NULL) {
 141                 s->len2 = len;
 142                 if (s->len2 > (s->shm_size - s->len1)) {
 143                         s->len2 = 0;
 144                         errno = ENOMEM;
 145                         return NULL;
 146                 }
 147                 s->ptr2 = s->shm_pointer + s->len1;
 148                 return s->ptr2;
 149         }
 150
 151         errno = ENOMEM;
 152         return NULL;
 153 }
 154
 155 static void smbd_shm_signing_free(TALLOC_CTX *mem_ctx, void *ptr)
 156 {
 157         struct smbd_shm_signing *s = talloc_get_type_abort(mem_ctx,
 158                                      struct smbd_shm_signing);
 159
 160         if (s->ptr2 == ptr) {
 161                 s->ptr2 = NULL;
 162                 s->len2 = 0;
 163         }
 164 }
 165
 166 /***********************************************************
 167  Called by server negprot when signing has been negotiated.
 168 ************************************************************/
 169
 170 bool srv_init_signing(struct smbd_server_connection *conn)
 171 {
 172         bool allowed = true;
 173         bool desired;
 174         bool mandatory = false;
 175
 176         struct loadparm_context *lp_ctx = loadparm_init_s3(conn, loadparm_s3_helpers());
 177         if (lp_ctx == NULL) {
 178                 DEBUG(10, ("loadparm_init_s3 failed\n"));
 179                 return false;
 180         }
 181
 182         /*
 183          * if the client and server allow signing,
 184          * we desire to use it.
 185          *
 186          * This matches Windows behavior and is needed
 187          * because not every client that requires signing
 188          * sends FLAGS2_SMB_SECURITY_SIGNATURES_REQUIRED.
 189          *
 190          * Note that we'll always allow signing if the client
 191          * does send FLAGS2_SMB_SECURITY_SIGNATURES_REQUIRED.
 192          */
 193
 194         desired = lpcfg_server_signing_allowed(lp_ctx, &mandatory);
 195         talloc_unlink(conn, lp_ctx);
 196
 197         if (lp_async_smb_echo_handler()) {
 198                 struct smbd_shm_signing *s;
 199
 200                 /* setup the signing state in shared memory */
 201                 s = talloc_zero(conn, struct smbd_shm_signing);
 202                 if (s == NULL) {
 203                         return false;
 204                 }
 205                 s->shm_size = 4096;
 206                 s->shm_pointer =
 207                         (uint8_t *)anonymous_shared_allocate(s->shm_size);
 208                 if (s->shm_pointer == NULL) {
 209                         talloc_free(s);
 210                         return false;
 211                 }
 212                 talloc_set_destructor(s, smbd_shm_signing_destructor);
 213                 conn->smb1.signing_state = smb_signing_init_ex(s,
 214                                                         allowed, desired, mandatory,
 215                                                         smbd_shm_signing_alloc,
 216                                                         smbd_shm_signing_free);
 217                 if (!conn->smb1.signing_state) {
 218                         return false;
 219                 }
 220                 return true;
 221         }
 222
 223         conn->smb1.signing_state = smb_signing_init(conn,
 224                                                     allowed, desired, mandatory);
 225         if (!conn->smb1.signing_state) {
 226                 return false;
 227         }
 228
 229         return true;
 230 }
 231
 232 void srv_set_signing_negotiated(struct smbd_server_connection *conn,
 233                                 bool allowed, bool mandatory)
 234 {
 235         smb_signing_set_negotiated(conn->smb1.signing_state,
 236                                    allowed, mandatory);
 237 }
 238
 239 /***********************************************************
 240  Returns whether signing is active. We can't use sendfile or raw
 241  reads/writes if it is.
 242 ************************************************************/
 243
 244 bool srv_is_signing_active(struct smbd_server_connection *conn)
 245 {
 246         return smb_signing_is_active(conn->smb1.signing_state);
 247 }
 248
 249
 250 /***********************************************************
 251  Returns whether signing is negotiated. We can't use it unless it was
 252  in the negprot.
 253 ************************************************************/
 254
 255 bool srv_is_signing_negotiated(struct smbd_server_connection *conn)
 256 {
 257         return smb_signing_is_negotiated(conn->smb1.signing_state);
 258 }
 259
 260 /***********************************************************
 261  Turn on signing from this packet onwards.
 262 ************************************************************/
 263
 264 void srv_set_signing(struct smbd_server_connection *conn,
 265                      const DATA_BLOB user_session_key,
 266                      const DATA_BLOB response)
 267 {
 268         bool negotiated;
 269         bool mandatory;
 270
 271         if (!user_session_key.length)
 272                 return;
 273
 274         negotiated = smb_signing_is_negotiated(conn->smb1.signing_state);
 275         mandatory = smb_signing_is_mandatory(conn->smb1.signing_state);
 276
 277         if (!negotiated && !mandatory) {
 278                 DEBUG(5,("srv_set_signing: signing negotiated = %u, "
 279                          "mandatory_signing = %u. Not allowing smb signing.\n",
 280                          negotiated, mandatory));
 281                 return;
 282         }
 283
 284         if (!smb_signing_activate(conn->smb1.signing_state,
 285                                   user_session_key, response)) {
 286                 return;
 287         }
 288
 289         DEBUG(3,("srv_set_signing: turning on SMB signing: "
 290                  "signing negotiated = %u, mandatory_signing = %u.\n",
 291                  negotiated, mandatory));
 292 }
 293